Crystal structure of bis(triethanolamine-kappa N-3,O,O ')nickel(II) bis(3-hydroxybenzoate) tetrahydrate

The reaction of 3-hydroxybenzoic (m-hydroxybenzoic) acid (MHBA), triethanolamine (TEA) and Ni(NO3)(2) in aqueous solution led to formation of the hydrated title salt, [Ni(C6H15NO3)(2)](C7H5O3)center dot 4H(2)O. In the complex cation, the Ni2+ ion is located on an inversion centre. Two symmetry-related TEA ligands occupy all coordination sites in an N,O,O'-tridentate coordination, leading to a slightly distorted NiN2O4 octahedron. Two ethanol groups of each TEA ligand form two five-membered chelate rings around Ni2+, while the third ethanol group does not coordinate to the metal atom. Two MHBA(-) anions in the benzoate form are situated in the outer coordination sphere for charge compensation. An intricate network of hydrogen bonds between the free and coordinating hydroxy groups of the TEA ligands, the O atoms of the MHBA(-) anions and the water molecules leads to the formation of a two-dimensional structure extending parallel to (010).